Food holding cabinet

ABSTRACT

A food holding cabinet for containing and spacedly supporting a vertical stack of trays. Trays are supported in spaced relation and are electromechanically elevated from a bottom tray receiving position to an uppermost tray position. An elevator is actuated to carry a tray upwardly to an uppermost available tray position. When it reaches that position, its direction of movement is automatically reversed, the tray is released, and the elevator returns to the bottom tray receiving position. Automatic close control over the humidity and temperature in the cabinet is achieved. Moisture is automatically added by vaporizing water if the humidity is too low and moisture is dumped by opening the cabinet to the ambient atmosphere if the humidity reaches too high a level. The cabinet is configured to minimize loss of heat and humidity when a cabinet door is opened to introduce or remove a tray.

United States Patent 1 1 Binks et a1.

[ Aug. 14, 1973 1 1 FOOD HOLDING CABINET 22 Filed: Nov. 15, 1971 [21] Appl. No.: 198,650

[52] US. Cl. 312/236, 312/250 51 1m. (:1. A47b 77/08, A47b 91/00 58 Field of Search 312/236, 229, 223,

[56] 1 References Cited UNITED STATES PATENTS 1,920,825 8/1933 Williams 312/306 X 3,170,541 2/1965 Werner 312/236 X 3,327,092 6/1967 Wilson 312/236 X 3,361,510 1/1968 McDermott 312/306 3,531,169 9/1970 Hoffman et a] 312/236 3,584,927 6/1971 Ott 312/236 X P mary Emminerfla ilB-fi li Attorney Max Dressler, Marshallwfsutker et al.

[57] 1 ABSTRACT A food holding cabinet for containing and spacedly supporting a vertical stack of trays. Trays are supported in spaced relation and are electromechanically elevated from a bottom tray receiving position to an uppermost tray position. An elevator is actuated to carry a tray upwardly to an uppermost available tray position. When it reaches that position, its direction of movement is automatically reversed, the tray is released, and the elevator returns to the bottom tray receiving position. Automatic close control over the hu-.

midity and temperature in the cabinet is achieved. Moisture-is automatically added by vaporizing water if the humidity is too low and moisture is dumped by '20 Claims, 16 DrawingFigures PATENTED AUG 14 I873 SHEEI 2 0F 6 PATENIEDm: 14 ran SHEET B [If 6 "unsw- This invention relates to a food holding cabinet and particularly to one which is adapted to provide a suitable environment internally for food contained in a vertical stack of trays supported therein. The cabinet defines an enclosed interior space in which the trays are supported, the trays being insertable into the enclosed space adjacent the bottom of the cabinet and being removable from the enclosed space at an uppermost tray position in the cabinet.

Food holding cabinets for a vertical stack of trays are known in the art. Such cabinets frequently provide support means for spacedly supporting a vertical stack of trays. A typical structure is illustrated in Stentz U.S. Pat. No. 3,205,033. Other cabinets have been suggested which provide tray-raising mechanisms, by which food-containing trays may be inserted into an enclosed cabinet space, such as at the base of the cabinet, and from which such trays may be removed at a different elevation, such as adjacent the top of the cabinet. A typical device of that character is illustrated in U.S. Pat. No. 3,531,169.

The food holding cabinet of this invention improves upon presently available food holding cabinets in a number of important respects.

In accordance with this invention, a food holding cabinet defining an enclosed interior space for containing a vertical stack of trays is provided with door means for closing access openings to the interior space. Trayraising or elevator means are provided for automatically elevating a tray from the bottom of the interior space to an uppermost tray position, from which the tray is adapted to be removed, as through a door at the front of the cabinet which is dimensioned and which is openable only to allow a tray supported at an uppermost tray position to be removed from the cabinet. The elevator means is electromechanically operated and requires no operator once it has been actuated.

The elevator means is actuated by a motor energizing switch. The motor drives suitable drive means, such as threaded drive shafts which carry tray retainers upwardly continuously and smoothly until a retained tray reaches an uppermost available position in the interior space. Once a tray is in the uppermost tray position, a further switch is operated automatically to return the tray retainers to a lowermost tray-receiving position. Accordingly, no operator is required to pump" trays from lower positions to upper positions, such as is the case with food cabinets illustrated in U.S. Pat. No. 3,531,169. The smooth continuous movement of the trays with the automatic elevator mechanism means eliminates jostling and disturbance of the product in the tray, and minimizes the possibility of causing the trays to cant out of their horizontal dispositions, thereby to dump food or to foul other interior portions of the cabinet assembly.

Furthermore, in accordance with this invention only one pair of opposed tray retainers is necessary to move a tray from the bottom to the top of the interior space, unlike tray-elevating systems of the character illustrated in U.S. Pat. No. 3,531,169.

The food holding cabinet of this invention also incorporates tray-supporting assemblies at each side of the cabinet which provide expansive four-point support for each of a vertical stack of trays and which also desirably provide uppermost tray supporting elements having expansive slide support surfaces for sliding support of a tray, thereby to facilitate its use until emptied and then its removal from the cabinet.

Desirably, the food holding cabinet of this invention also provides means for controlling the humidity and temperature in the cabinet. The humidity is controlled at a predetermined level by a humidistat assembly which functions to admit water and to vaporize that water when the humidity is too low, and which also functions to dump excess moisture when the humidity is too high. Additionally, means for heating the air within the cabinet are provided], and a blower is provided to circulate the air and moisture so that all sections of the interior space in the cart are uniformly heated and humidifed, and at desired temperature and humidity levels.

The door means in the cabinet are preferably at the front, and comprise a large intermediate service door, through which door, interior removable parts may be removed for servicing, and through which door the cabinet may be cleaned. The door means also includes shallow top and bottom doors which close access openings which are high enough only to permit removal from or insertion into the cabinet, respectively, of a single tray. The use of shallow access openings minimizes the loss of heat and humidity when a tray is introduced into the cabinet or when the cabinet must be opened for removal of food from a tray, or for removal of a tray. Indeed, the upper and lower doors are preferably positioned so that a tray may be removed through the upper door only from an uppermost tray supporting means, and may be inserted through the lower door only into opposed tray retainers positioned adjacent the bottom of the interior space, respectively.

Further objects, features and advantages of this invention will become apparent from the following description and drawings, of which:

FIG. I is a perspective view ofa food holding cabinet of this invention;

FIG. 2 is a perspective view similar to FIG. 1, show ing a top door open;

FIG. 3 is a perspective view similar to FIG. I, showing a bottom door open;

FIG. 4 is a rear elevational view of the food holding cabinet of FIG. 1, partially broken away;

FIG. 5 is a bottom view of the food holding cabinet of FIG. 1;

FIG. 6 is a fragmentary view illustrating a humidity control and gauge subassembly;

FIG. 7 is a fragmentary view adjacent the lower end of an elevator mechanism;

FIG. 8 is a cross-sectional view, partially broken away, taken substantially along the line 8-8 of FIG. 5;

FIG. 9 is a plan view, partially broken away, of the food holding cabinet of FIG. 1;

FIG. 10 is a fragmentary view, similar to FIG. 9, with the bottom door open;

FIG. 11 is a side elevational view of elevator and tray support assemblies of the food holding cabinet of FIG.

FIG. 12 is a cross-sectional view taken substantially along the line l2--12 of FIG. 11;

FIG. 13 is a cross-sectional view taken substantially along the line 13-13 of FIG. 11;

FIG. 14 is a cross-sectional view taken substantially along the line 14-44 of FIG. 1;

FIG. 15 is a fragmentary, partially schematic view taken substantially along the line 15-15 of FIG. 4; and

FIG. 16 is a schematic wiring diagram of the food holding cabinet of FIG. 1.

Referring first to FIGS. 1 to 5, a food holding cabinet of this invention is roller supported and comprises insulated side panels 12, an interior top panel 13 (FIG. 8), an exterior back panel 14, an interior back panel 15, a bottom panel 16 and a top having a top work surface 17. The panels 12, 13, and 16, together with the doors to be described, define a generally rectangular enclosed interior space or compartment C. The top of the cabinet also mounts a console section providing a plurality of storage compartments 18, a control panel 19, and a humidity control assembly cover 20. The front 21 of cabinet 10 defines a series of access openings, each closed by an insulated door, including a bot tom door 22, a top door 24 and a large intermediate service door 26 which may incorporate a glass viewing panel 27. Each of the doors is hingedly mounted on the cabinet 10 and each is provided with a handle 28 to facilitate opening and closing. The cabinet 10 is mounted on casters 30 to assist in its movement from place to place as desired.

Trays T for carrying food, such as chicken, are pro portioned to be placed in food holding cabinet 10 through bottom door 22. Trays T mount upstanding tray bars B which serve as handles, spacers and contact members. Tray bars B extend from the front to the back of the tray at each side and the central portions are parallel to the tray bottom to provide expansive contact with a superposed tray bottom. The central portions are spaced well above the tray rim. In a stack, the spacer bars B are closely adjacent the next upper tray and are positioned to engage and lift the next upper tray when the trays are lifted by an elevator means.

An elevator means is provided to move trays T from the bottom of the interior space upwardly in cabinet 10 to an uppermost tray position for removal from top door 24. Elevator mechanism comprises a reversing motor 42 having an appropriate reducing gear assembly suitably mounted on bottom panel 16. A pair of drive shafts 44 extend sidewardly, as is clearly illustrated by FIGS. 4 and 5. v

At their outer extremities drive shafts 44 are supportingly journaled on the cabinet 10 and are provided with suitable drive means 45 such as bevel gears for the driving of threaded elevator shafts 48. The drive means may each drive a drive coupling 49 defining a rectangular opening into which a lowermost drive pin segment 50 of an elevator shaft 48 is removably insertable, for removable interconnection with the drive shafts 44 through drive coupling 49 and drive means 45.

Elevator shafts 48 are threaded so that when they are rotated they will drive elevators 52 therealong. Each elevator 52 comprises a threaded central bushing 54 having threads which are complementary to those of elevator shafts 48. Each bushing 54 is unified with a frame 56 which pivotally mounts a pair of trayengaging tray retainer fingers 58 (FIGS. 13 and 14), and which fingers 58 are biased normally from the dotted line to the full line position of FIG. 14 by torsion springs 60.

Opposed pairs of fingers 58 normally are positioned to supportingly engage opposite side edges of a tray rim in notches 62 and to hold, receive and stabilize the tray thereby to prevent it from tipping and tilting as the elevators 52 move continuously from a lower position to an uppermost tray position near the very top of the interior space in the cabinet, such as from the lowermost tray position to the uppermost tray position illustrated in FIG. 8. As the elevators 52 move downwardly, because notches 62 are suitably dimensioned, the tray rim cams and biases the retainer fingers 58 outwardly against the force of torsion springs 60 (to the dotted line position of FIG. 14), thereby to release a tray to to permit return of elevators 52 to the lowermost position illustrated in FIG. 8.

At its uppermost edge, elevator shaft 48 is journaled on a bracket 64. Bracket 64 may be removably secured to a side panel 12, as by suitable mounting means, such as shoulder bolts 65 (FIG. 9), which mate with shaped apertures 66 (FIGS. 9 and 11). By utilizing the removable bracket 64 atone end and the lower insertable elevator shaft drive pin segments 50 to fix each of the opposed elevator shafts 48 in position, the elevator shaft assemblies may be easily removed from the cabinet 10 through the access opening closed by door 26, to facilitate their cleaning and to facilitate cleaning of the cabinet. It should be noted that the proximity of the frames 56 to the side panels 12 prevents significant oscillation of an elevator 52 about the axis of a shaft 48.

The food holding cabinet of this invention is adapted to hold a superposed slightly spaced stack of trays. In the embodiment illustrated, the cabinet 10 may hold a stack of as many as nine trays T, each loaded with food. Assuming there are nine trays in the cabinet, the lowermost tray would be supported and held by the tray retainer fingers 58 and on slide guides 102 on the bottom cabinet panel. The next eight trays would be supported on tray-supporting assemblies 70.

A pair of tray-supporting assemblies 70 is removably mounted at each side of cabinet 10 (see FIGS. 8, 9 and 11). These are separate from the elevator mechanism and therefore they are less susceptible to binding due to dirt and the like. Each supporting assembly comprises a sheet metal frame member 72 formed to define a channel 73 as is illustrated in FIG. 12. Suitable mounting slots 74 proportioned to receive and be seated upon mounting pins 74A are provided. At the bottom of each frame member 72, a suitable notch 76 is provided. This cooperates with a further mounting pin 76A (FIG. 7) to hold the lower end of the frame member against the side panel 12. In that manner frame members 72 are removably secured to side panels 12.

To make certain that brackets 64 and frame assemblies 70 are not inadvertently displaced upwardly, a retainer plate is provided at each side of the cabinet (see FIG. 12). Each is removably secured to a side panel 12 and provides downwardly extending shoulders 75 which confront upper edges of a bracket 64 and frame member 72. When a retainer plate 75 is secured, as by bolts 75A, the underlying bracket 64 and assemblies 70 may not be moved upwardly or removed.

Each frame member 72 mounts a vertical stack of tray-support elements 78. Each tray-support element 78 is generally U-shaped and is proportioned normally to project inwardly from the cabinet side panel into the positions in the cabinet interior space illustrated in FIG. 8. Because each element 78 is mounted on hinge pins 80 (which are positioned in complementary apertures 81 in frame members 72), they are biasable outwardly, so that as trays T are moved upwardly by elevators 52, elements 78 will not impede passage of the trays upwardly. Elements 78 are, however, proportioned so that they are biased by gravity normally into the positions of FIG. 8. i

As stated, a pair of tray-supporting assemblies 70 are provided at each side of food holding cabinet 10. They are positioned to straddle the elevator shafts 48. Because of their positioning, and because of the width of the support elements 78 (see FIG. 9), expansive fourpoint support for a tray is provided, and for each of a stack of seven vertically superposed trays.

At each side the tray-supporting assemblies 70 mount an eighth tray support means or slide support assembly 90. Slide support assembly 90 is best seen in FIGS. 8 and 9 and as there illustrated comprises a pair of slide support elements or sections 92 interconnected by a generally-U-shaped bracket member 94. Each slide support assembly is oscillatably mounted on a pair of frame members 72 by a pair of pins 96, one of which is mounted in an aperture in each of the frames 72.

Bracket member 94 bridges sections 92 and is shaped and positioned so that it does not interfere with the operation of elevators 52. Slide sections 92 provide expansive upper slide support surfaces for sliding support of a tray rim, as is illustrated in FIG. 8. The depending limbs 95 of bracket 94 are spaced closely adjacent the lateral edge of the tray to cooperate with the upper slide surfaces to guide a tray as it is moved forwardly and outwardly through top door 24 and thence rearwardly into a storage position on the upper slide surfaces 92.

In use, as a tray moves upwardly past support elements 78 and to the level of slide support sections 92, a tray rim will contact the innermost edges of the slide sections to bias the slide support assemblies 90 upwardly and outwardly about the axis of pins 96 to permit the tray rim to pass the elevation of support sections 92. After the tray has passed that elevation, gravity causes the slide assemblies 90 to return to the position illustrated in FIG. 8 so that when the elevator motor is reversed, the tray rim will return to the level of slide support sections 92 to be supported as illustrated in FIG. 8. A slide assembly 90 is mounted in the manner described at eachside of the cabinet 10.

When the food holding cabinet l0is to be provided with a tray or trays T, the trays may first be filled or loaded as desired with a food product. Where the food product has been fried, it may be desirable to supply the trays with draining racks D (see FIGS. 2 and 3).

A first tray T is inserted through door 24 for support on slide sections 92. Subsequent trays are inserted through bottom door 22 for elevation to uppermost available positions, either at slide sections 92 if that position has been made available by removal of a tray therefrom, or to a next lower available position.

To fill the cabinet 10 with trays, the bottom door 22 is opened. The handle 28 may be provided with an upper hook element 29 (see FIGS. 1 and 2) adapted to engage with a tray rim, so that the door may be pulled open by a tray. A tray T is positioned on the inner door surface and is slid inwardly. So that the level of the tray rim will be appropriate for engagement within the notches 62 of tray retainers 58, the inner surface of the door 22 may be provided with suitable slide shims 100 and the bottom panel of the cabinet may be provided with slide guides 102 (see FIGS. 9 and 10). The tray is then fully inserted from the position illustrated in FIG.

3 and, thereafter, door 22 is closed and is held in its closed position by suitable latching means (not shown). Indeed, where desired, a suitable interlock may be provided so that as the trays are moving from a lower position to an upper position, none of the doors 22, 24 or 26 may be opened. The interlock may also serve a safety function, i.e., to prevent operation of the elevator mechanism unless all of the doors are closed or if a door is opened during elevation.

When all of the doors have been suitably closed, a start switch 104 is operated to actuate the elevator assemblies. Switch 104 energizes the capacitor motor 42, causing elevator shafts 48 to rotate continuously in a first direction to move elevators 52 upwardly along shafts 48. An associated tray will be carried upwardly past tray-support elements 78 and the tray-support elements will be cammed outwardly against gravity, to return to the positions illustrated in FIG. 8 after the tray has passed their elevation. When a tray carried by trayretaining fingers 58 reaches the tray already positioned on slide support assemblies 90, the tray bars B contact the lower surface of that upper tray and elevate that upper tray slightly until its rim contacts and slightly displaces a reversing limit switch lever 105. Lever 105 is pivotally connected to a rod 107 (FIG. 7) and is pivotally mounted on the tray supporting assembly 70. Rod 107 extends downwardly within, the frame member 72 for reciprocable movement and for operating reversing switch 106. When lever 105 is: pivotally displaced, switch 106 signals that the newly elevated tray has reached the uppermost available tray position and automatically causes the direction of the motor to reverse, hence counterrotating the elevator shafts 48 to drive the elevators 52 downwardly. As the elevators move downwardly, the rim of the upper tray T again contacts the upper surfaces of slide support sections 92 and is stopped thereby. The rim of the lower tray engages support segments 82 stopping the downward movement of that tray. The tray retainer fingers 58 cam outwardly to the dotted line position illustrated in FIG. 14, thereby to release that tray. When the elevators 52 reach the lowermost tray receiving position of FIG. 8, a lower limit switch 108 is engaged, which stops the motor.

Although further trays are normally inserted through door 22 after the elevators have returned to their lowermost position, it should be noted that the retainer fingers 58 need not have returned to their lowermost positions before inserting a new tray through door 22. If a tray has been so positioned, when fingers 58 contact the rim, they will cam outwardly and will then move downwardly until the tray rim snaps into notches 62, at which time the tray is ready to be elevated.

When a further tray is to be raised, start switch 104 is actuated and the tray is carried upwardly until bars B contact the bottom of the lowermost of the upper trays and lift the upper trays slightly until the uppermost tray rim again contacts reversing limit switch lever 105, again causing the motor assembly to reverse its direction of rotation, causing the elevators to move downwardly again. The uppermost tray is again held on slide sections 92, whereas the next lower trays drop to positions where they are seated on the support segments 82 of tray-support elements 78. When the tray rim is so intercepted, the tray retainer fingers 58 are cammed outwardly to the position shown in dotted line in FIG. 14 and the elevators 52 again return to the posi tion illustrated in FIG. 8. When the uppermost tray is removed, a cycle of operation will result in thenext uppermost tray being carried upwardly past slide support sections 92, camming them outwardly in the manner described above until the tray passes the elevation of those sections, at which time gravity returns them to their supporting positions.

Successive and additional trays may be similarly raised to the uppermost available position in the food holding cabinet. Indeed a full complement of trays, such as eight may be elevated as necessary by the elevator mechanism.

In devices of the character illustrated in US. Pat. No. 3,531,169, it is difficult to elevate more than four or five trays because of the mechanical lifting system utilized.

When food is to be withdrawn from food holding cabinet 10, the top door 24 is opened, and the tray T supported on the upper surface of slide sections 92 is slid forwardly, such as to the position illustrated in FIG. 2. The inner surface of door 24 which may also mount shims 100, the expansive upper surfaces of slide sections 92 and slotted tray guides 93 provide substantial sliding support of the tray. Tray guides 93 are positioned at the front of the cabinet at each side and the slots 93' thereof slidably accommodate and retain the tray rim at each side as the tray is moved in and out. Because the width of the tray with respect to the cabinet is disposed sideways, the tray need be moved outwardly minimally to gain access to a given quantity of evenly distributed food product. After the food desired is removed from the tray, if food still remains in the tray, it is pushed rearwardly into the cabinet and the top door 24 is again closed. When the uppermost tray T has been emptied, it is removed. At that time, the next tray may be brought to the uppermost position to be supported on slide sections 92 by actuating the start switch 104. When that occurs, the lowermost of the trays in the cabinetwill be gripped and received at its rim in finger notches 62, and the elevators 52 will then carry all of the trays upwardly automatically to the uppermost available positions.

It will be noted that the lower and upper'doors are dimensioned and positioned so that they confront the tray retainer fingers and tray slide support sections, respectively, so that they serve as slide surfaces when inserting and removing trays, and that their vertical dimensions are such that only one tray, i.e., the tray retained in or to be retained in retainer finger notches 62, or the tray slidingly supported on slide surfaces 92, may be inserted or removed, respectively, through the doors. That minimizes the amount of heat and humidity lost when the doors are opened, an important advantage to the food holding cabinet of this invention.

To ready food holding cabinet for use, a main power switch 110 is turned on to provide power from power source 109, a power-on light 1 12 is energized, and motor 120 for circulating blower 122 is energized. Assuming that the cabinet is cold, a thermostat 114 having a sensor 114' closes a circuit to energize resistance heater 116 and the adding heat light 118. Blower 122 circulates air through the cabinet interior blowing it across heater 1 16 and between the space between inner back panel and baffle panel 124. Baffle panel 124 is removably mounted on baffle brackets 126 and mounts spacer brackets 128 to maintain a predetermined spacing between inner back panel 15 and baffle panel 124. Brackets 128 also serve as a rear bearing surface for the pans.

As stated, means are provided for closely controlling the humidity in the compartment C of cabinet 10. To that end a humidity control assembly 129 (FIG. 6) is provided. It mounts a pair of humidistats 130 and 150, each containing its own sensor and each being suitably adjustable to selectively determine upper and lower humidity limits via adjustment knobs 162 and 161, respectively. Assembly 129 is mounted so that it depends into compartment C (FIG. 8) and so that the humidistats may be blanketed in the atmosphere in compartment C. The side walls and bottom wall of assembly 129 are perforated (see FIG. 8) to permit the compartment atmosphere to circulate through the assembly 129 and over the humidistat sensors.

Assuming that the humidity is too low in the cabinet, a humidistat 130 closes to energize timer motor 142 and to light an adding moisture" light 136. Timer motor 142 runs through a predetermined cycle. Initially it closes cam operated switch 132 and holds that switch closed for its entire cycle. During the course of the cycle it closes cam operated switch 144, as for example for three seconds, to energize solenoid operated water valve 134 to admit water from supply pipe 141 into vaporizing trough 140, after which switch 144 is opened again. When the cycle is completed switch 132 opens. Assuming the humidity is still too low, humidistat 130 will cause the sequence described to be repeated until the humidity in the cabinet reaches a predetermined level.

Each time water is supplied to trough it is vaporized by heat supplied by a resistance heater 146. I-leater 146 is controlled by a thermostat 148 through a sensor 148. Resistance heater 146 is embedded in the trough body.

A further humidistat 150 is provided to control a dump valve assembly 152. When the humidity reaches toohigh a level, as when hot, steaming food is introduced to the cabinet, a dump valve is opened by humidistat 150 to allow humid air to escape from the cabinet, by placing the interior space in communication with the outside of the cabinet thereby reducing the humidity to a preset level.

As illustrated in FIGS. 9 and 15, dump valve assembly 152 comprises a dump valve or flap element 153 which is pivotally mounted on the cabinet 10 on a rod 153A to open and close a port 154 (see FIG. 9) in interior top panel 13. The flap element is moved by a solenoid 155 which is controlled by and responsive to humidistat 150. A sheet metal hood member 156 is provided to define a duct (having a top 156A, sides 156B, and a front 156C) with panel 13 leading to discharge opening 157.

It should be noted that humidistats 130 and 150 are adjustable by adjustment knobs 161 and 162, respectively, to predeterminable levels within preselected ranges and that a hygrometer gauge 160 (FIG. 6) for indicating humidity and temperature levels in the interior space or compartment C is provided behind cover 20.

It is clear that close control over the humidity and temperature is provided in a compartment C in a cabinet 10 of this invention, making it possible to hold food for longer periods of time than was heretofore possible, and without having it deteriorate in quality.

The elevator mechanism, as previously stated, is actuated by a start switch 104. If all of the doors are closed, magnetically operated door interlock switches 158 will energize a relay 158A which will close switch 1588. That will permit capacitor motor 42 to be operated. The ready to raise" light 159 will be energized when the elevator is in a full down position.

When the operating button of start switch 104 is operated, it energizes relay 104A. Relay 104A then moves switches 1048 and 104C from the full line positions illustrated in FIG. 16 to the dotted line positions there shown. Assuming interlock switch 1588 is closed, then the elevator capacitor motor 42 drives the elevator upwardly. As soon as lifting begins, lower limit switch 108 moves from the full line to the dotted line position illustrated in FIG. 16, and the light 159 is extinguished.

When limit switch 106 is operated, it opens the circuit to relay 104A, causing switches 1048 and 104C to return to their full line positions. As a result of that, the motor direction reverses driving the elevator downwardly. When the lower limit switch 108 is contacted again, that switch opens and returns to the full line position of FIG. 16, the motor stops and the light 159 is energized. If during a cycle of operation one ormore doors are opened, the motor 42 will stop. When the doors are closed, the cycle will continue from the point at which it was interrupted.

Presumably one or more doors will be opened for trays to be placed in or removed from the cabinet. When all of the doors are again closed, relay 158A will be energized and the elevator mechanism will be ready to operate through another cycle.

Only a presently preferred embodiment of this invention has been illustrated and described, although the invention is susceptible of embodiment in many different forms. it is to be understood that the present disclosure is intended to be an exemplification of the principles of the invention, and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

What is claimed is:

1. A food holding cabinet defining an enclosed interior space for containing a vertical stack of trays and having door means forclosing access openings to said interior space, a tray supporting assembly at each side of said cabinet, each said tray supporting assembly comprising a stack of tray supporting elements that normally project inwardly of said interior space toward the opposite side of said cabinet, said tray supporting elements being biasable outwardly to permit a tray to move upwardly therepast, an elevator assembly for elevating a tray from the bottom of said interior space to an uppermost tray position in said interior space past a plurality of said tray supporting elements, switch means for actuating said elevator assembly, said elevator assembly comprising opposed tray retainers for engaging opposite side portions of a tray and elevator means mounting said tray retainers for continuously elevatin g said tray retainers until a tray reaches an uppermost available tray position in said interior space, means adjacent said uppermost tray position for signalling when a tray has reached the uppermost available tray position and means responsive thereto for automatically lowering said tray retainers to a lowermost tray receiving position.

2. A food holding cabinet in accordance with claim 1, wherein said elevator means mounting said tray retainers comprises a rotatable threaded shaft at each side of said interior space, and motor means for rotating said threaded shafts.

3. A food holding cabinet in accordance with claim 2 wherein said motor means is a reversible motor and said switch means actuates said motor to rotate said threaded shaft in a first direction to elevate said tray retainers and said signalling means causes said motor to reverse its direction of rotation to rotate said shaft in the opposite direction to return said tray retainers to said lowermost tray receiving position.

4. A food holding cabinet in accordance with claim 1 wherein said tray supporting assemblies are removably mounted in said cabinet.

5. A food holding cabinet in accordance with claim 1 wherein pairs of stacks of tray supporting elements provide four-point support for each of a stack of trays.

6. A food holding cabinet in accordance with claim 1 wherein pairs of stacks of tray supporting elements provide four-point support for each of a stack of trays and an uppermost supporting element having an expansive slide support surface for sliding support of a tray at each side of said cabinet.

7. A food holding cabinet in accordance with claim 6 wherein said door means comprises a door at the front of said cabinet which is openab le to allow only a tray supported on said slide support surfaces to be moved forwardly and outwardly through said door.

8. A food holding cabinet in accordance with claim 1 wherein said door means comprises a door at the front of said cabinet which is openable to allow only a tray supported on the uppermost of said tray supporting elements to be moved forwardly and outwardly through said door. i

9. A food holding cabinet in accordance with claim 1 wherein said door means comprises a door at the front of said cabinet which is openable to allow a tray to be inserted only into said tray retainers below said tray supporting elements.

10. A food holding cabinet in accordance with claim 1 further including means for controlling the humidity in said cabinet generally uniformly throughout, said humidity controlling means comprising a humidistat in said cabinet, valve means for supplying water to the interior space in said cabinet, means operatively connected to and responsive to said humidistat for operating said valve means to admit water to said cabinet, means for controllably heating and vaporizing the water in said cabinet, and blower :means in said cabinet for circulating warm, moist air through said interior space in said cabinet.

1 1. A food holding cabinet defining an enclosed interior space for containing a vertical stack of trays and having door means for closing access openings to said interior space, a tray supporting assembly at each side of said cabinet, each said tray supporting assembly comprising a stack of tray supporting elements that normally project inwardly of said interior space toward the opposite side of said cabinet and which are biasable outwardly of said interior space to permit a tray to move upwardly therepast, an elevator assembly for elevating a tray from the bottom of said interior space to an uppermost tray position in said interior space past a plurality of said tray supporting elements, said elevator assembly comprising opposed tray retainers for engaging opposite side portions of a tray, and elevator means mounting said tray retainers and for elevating said tray retainers from the bottom to the top of the interior space, and means for controlling the humidity in said interior space generally uniformly throughout, said humidity controlling means comprising a humidistat in said cabinet, valve means for supplying water to the interior space in said cabinet, means operatively connected to and responsive to said humidistat for operating said valve means to admit water to said cabinet, means for vaporizing the water admitted into said cabinet, and blower means for circulating air through said interior space in said cabinet.

12. A food holding cabinet in accordance with claim 11, further including a temperature sensing element in said interior space and heating means operatively connected to and responsive to said temperature sensing element for heating the air in said cabinet.

13. A food holding cabinet in accordance with claim 12 wherein said door means comprises a door at the front of said cabinet which is openable to allow only a tray supported at said uppermost tray position to be moved forwardly through said door, and a second door at the front of said cabinet which is openable to allow a tray to be inserted onlyinto said tray retainers below said tray supporting elements.

14. A food holding cabinet in accordance with claim 11 further including a dump valve, said dump valve being operable to place the interior space in communication with the external ambient atmosphere in response to a signal from said humidistat thereby to reduce the humidity level in said interior space by allowing humid air to leave said interior space.

15. A food holding cabinet defining an enclosed interior space for containing a vertical stack of trays and having door means for closing access openings to said interior space, a tray supporting assembly at each side of said cabinet, each said tray supporting assembly comprising a stack of tray supporting elements that normally project inwardly of said interior space toward the opposite side of said cabinet, said tray supporting elements being biasable outwardly to permit a tray to move upwardly therepast, an elevator assembly for elevating a tray from the bottom of said interior space to an uppermost tray position in said interior space past a plurality of said tray supporting elements, switch means for actuating said elevator assembly, said elevator assembly comprising opposed tray retainers for engaging opposite side edges of a tray and elevator means mounting said tray retainers for continuously elevating said tray retainers until a tray reaches an uppermost available tray position in said interior space, means adjacent said uppermost tray position for signaling when a tray has reached the uppermost available tray position and means responsive thereto for automatically returning said tray retainers to a lowermost tray receiving position, means for controlling the humidity in said cabinet generally uniformly throughout, said humidity controlling means comprising a humidistat in said cabinet, valve means for supplying water to the interior space of said cabinet, means operatively connected thereto and responsive to said humidistat for operating said valve means to admit water to said cabinet, means for vaporizing the water admitted to said cabinet, and blower means for circulating air through the interior space in said cabinet, and said door means comprising a door at the front of said cabinet which is openable to allow only a tray supported at said uppermost tray position to be moved forwardly through said door, and a second door at the front of said cabinet which is openable to allow a tray to be inserted only into said tray retainers below said tray supporting elements, and a third larger door between said first and second doors.

16. A food holding cabinet in accordance with claim 15 wherein said mounting means comprises a rotatable threaded shaft at each side of said interior space, and a reversible motor for rotating said threaded shafts, said switch means actuating said motor to rotate said threaded shafts in a first direction to move said tray retainers upwardly, and said signaling means reversing the direction of rotation of said motor to move said tray retainers downwardly to said lowermost tray receiving position.

17. A food holding cabinet in accordance with claim 1 further including a plurality of vertically superposed trays supported on said tray supporting elements, each said tray having spacer means positioned closely adjacent the next upper tray for engaging and lifting the next upper tray when said elevator means is elevated.

18. A food holding cabinet defining an enclosed inte' rior space for containing a vertical stack of trays and having door means for closing access openings to said interior space, a tray supportingassembly at each side of said cabinet, each said tray supporting assembly comprising a stack of tray supporting elements that normally project inwardly of said interior space toward the opposite side of said cabinet, said tray supporting elements being biasable outwardly to permit a tray to move upwardly therepast, an elevator assembly for elevating a tray from the bottom of said interior space to an uppermost tray position in said interior space past a plurality of said tray supporting elements, said elevator assembly comprising opposed tray retainers defining notch means for receiving opposite side portions of a tray and elevator means mounting said tray retainers for movement out of engagement with said side portions to release a tray, for elevating said tray retainers until a tray reaches an uppermost available tray position in said interior space and for returning said tray retainers to a lowermost tray receiving position.

19. A food holding cabinet in accordance with claim 18 wherein said tray retainers comprise opposed fingers pivotally mounted on said elevator means, and said notch means are defined by said fingers, said fingers being normally biased into tray side portion engaging positions to hold and stabilize a tray to prevent it from tipping and being biasable outwardly out of engagement with said side portions,

20. A food holding cabinet in accordance with claim 18 further including a plurality of vertically superposed trays supported on said tray supporting elements, each said tray having spacer means positioned closely adjacent the next upper tray and engaging and lifting the next upper tray when said elevator means is elevated. I i 1|! 1U 

1. A food holding cabinet defining an enclosed interior space for containing a vertical stack of trays and having door means for closing access openings to said interior space, a tray supporting assembly at each side of said cabinet, each said tray supporting assembly comprising a stack of tray supporting elements that normally project inwardly of said interior space toward the opposite side of said cabinet, said tray supporting elements being biasable outwardly to Permit a tray to move upwardly therepast, an elevator assembly for elevating a tray from the bottom of said interior space to an uppermost tray position in said interior space past a plurality of said tray supporting elements, switch means for actuating said elevator assembly, said elevator assembly comprising opposed tray retainers for engaging opposite side portions of a tray and elevator means mounting said tray retainers for continuously elevating said tray retainers until a tray reaches an uppermost available tray position in said interior space, means adjacent said uppermost tray position for signalling when a tray has reached the uppermost available tray position and means responsive thereto for automatically lowering said tray retainers to a lowermost tray receiving position.
 2. A food holding cabinet in accordance with claim 1, wherein said elevator means mounting said tray retainers comprises a rotatable threaded shaft at each side of said interior space, and motor means for rotating said threaded shafts.
 3. A food holding cabinet in accordance with claim 2 wherein said motor means is a reversible motor and said switch means actuates said motor to rotate said threaded shaft in a first direction to elevate said tray retainers and said signalling means causes said motor to reverse its direction of rotation to rotate said shaft in the opposite direction to return said tray retainers to said lowermost tray receiving position.
 4. A food holding cabinet in accordance with claim 1 wherein said tray supporting assemblies are removably mounted in said cabinet.
 5. A food holding cabinet in accordance with claim 1 wherein pairs of stacks of tray supporting elements provide four-point support for each of a stack of trays.
 6. A food holding cabinet in accordance with claim 1 wherein pairs of stacks of tray supporting elements provide four-point support for each of a stack of trays and an uppermost supporting element having an expansive slide support surface for sliding support of a tray at each side of said cabinet.
 7. A food holding cabinet in accordance with claim 6 wherein said door means comprises a door at the front of said cabinet which is openable to allow only a tray supported on said slide support surfaces to be moved forwardly and outwardly through said door.
 8. A food holding cabinet in accordance with claim 1 wherein said door means comprises a door at the front of said cabinet which is openable to allow only a tray supported on the uppermost of said tray supporting elements to be moved forwardly and outwardly through said door.
 9. A food holding cabinet in accordance with claim 1 wherein said door means comprises a door at the front of said cabinet which is openable to allow a tray to be inserted only into said tray retainers below said tray supporting elements.
 10. A food holding cabinet in accordance with claim 1 further including means for controlling the humidity in said cabinet generally uniformly throughout, said humidity controlling means comprising a humidistat in said cabinet, valve means for supplying water to the interior space in said cabinet, means operatively connected to and responsive to said humidistat for operating said valve means to admit water to said cabinet, means for controllably heating and vaporizing the water in said cabinet, and blower means in said cabinet for circulating warm, moist air through said interior space in said cabinet.
 11. A food holding cabinet defining an enclosed interior space for containing a vertical stack of trays and having door means for closing access openings to said interior space, a tray supporting assembly at each side of said cabinet, each said tray supporting assembly comprising a stack of tray supporting elements that normally project inwardly of said interior space toward the opposite side of said cabinet and which are biasable outwardly of said interior space to permit a tray to move upwardly therepast, an elevator assembly for elevating a tray from the bottom oF said interior space to an uppermost tray position in said interior space past a plurality of said tray supporting elements, said elevator assembly comprising opposed tray retainers for engaging opposite side portions of a tray, and elevator means mounting said tray retainers and for elevating said tray retainers from the bottom to the top of the interior space, and means for controlling the humidity in said interior space generally uniformly throughout, said humidity controlling means comprising a humidistat in said cabinet, valve means for supplying water to the interior space in said cabinet, means operatively connected to and responsive to said humidistat for operating said valve means to admit water to said cabinet, means for vaporizing the water admitted into said cabinet, and blower means for circulating air through said interior space in said cabinet.
 12. A food holding cabinet in accordance with claim 11, further including a temperature sensing element in said interior space and heating means operatively connected to and responsive to said temperature sensing element for heating the air in said cabinet.
 13. A food holding cabinet in accordance with claim 12 wherein said door means comprises a door at the front of said cabinet which is openable to allow only a tray supported at said uppermost tray position to be moved forwardly through said door, and a second door at the front of said cabinet which is openable to allow a tray to be inserted only into said tray retainers below said tray supporting elements.
 14. A food holding cabinet in accordance with claim 11 further including a dump valve, said dump valve being operable to place the interior space in communication with the external ambient atmosphere in response to a signal from said humidistat thereby to reduce the humidity level in said interior space by allowing humid air to leave said interior space.
 15. A food holding cabinet defining an enclosed interior space for containing a vertical stack of trays and having door means for closing access openings to said interior space, a tray supporting assembly at each side of said cabinet, each said tray supporting assembly comprising a stack of tray supporting elements that normally project inwardly of said interior space toward the opposite side of said cabinet, said tray supporting elements being biasable outwardly to permit a tray to move upwardly therepast, an elevator assembly for elevating a tray from the bottom of said interior space to an uppermost tray position in said interior space past a plurality of said tray supporting elements, switch means for actuating said elevator assembly, said elevator assembly comprising opposed tray retainers for engaging opposite side edges of a tray and elevator means mounting said tray retainers for continuously elevating said tray retainers until a tray reaches an uppermost available tray position in said interior space, means adjacent said uppermost tray position for signaling when a tray has reached the uppermost available tray position and means responsive thereto for automatically returning said tray retainers to a lowermost tray receiving position, means for controlling the humidity in said cabinet generally uniformly throughout, said humidity controlling means comprising a humidistat in said cabinet, valve means for supplying water to the interior space of said cabinet, means operatively connected thereto and responsive to said humidistat for operating said valve means to admit water to said cabinet, means for vaporizing the water admitted to said cabinet, and blower means for circulating air through the interior space in said cabinet, and said door means comprising a door at the front of said cabinet which is openable to allow only a tray supported at said uppermost tray position to be moved forwardly through said door, and a second door at the front of said cabinet which is openable to allow a tray to be inserted only into said tray retainers below said tray supporting elements, and a third larger door between sAid first and second doors.
 16. A food holding cabinet in accordance with claim 15 wherein said mounting means comprises a rotatable threaded shaft at each side of said interior space, and a reversible motor for rotating said threaded shafts, said switch means actuating said motor to rotate said threaded shafts in a first direction to move said tray retainers upwardly, and said signaling means reversing the direction of rotation of said motor to move said tray retainers downwardly to said lowermost tray receiving position.
 17. A food holding cabinet in accordance with claim 1 further including a plurality of vertically superposed trays supported on said tray supporting elements, each said tray having spacer means positioned closely adjacent the next upper tray for engaging and lifting the next upper tray when said elevator means is elevated.
 18. A food holding cabinet defining an enclosed interior space for containing a vertical stack of trays and having door means for closing access openings to said interior space, a tray supporting assembly at each side of said cabinet, each said tray supporting assembly comprising a stack of tray supporting elements that normally project inwardly of said interior space toward the opposite side of said cabinet, said tray supporting elements being biasable outwardly to permit a tray to move upwardly therepast, an elevator assembly for elevating a tray from the bottom of said interior space to an uppermost tray position in said interior space past a plurality of said tray supporting elements, said elevator assembly comprising opposed tray retainers defining notch means for receiving opposite side portions of a tray and elevator means mounting said tray retainers for movement out of engagement with said side portions to release a tray, for elevating said tray retainers until a tray reaches an uppermost available tray position in said interior space and for returning said tray retainers to a lowermost tray receiving position.
 19. A food holding cabinet in accordance with claim 18 wherein said tray retainers comprise opposed fingers pivotally mounted on said elevator means, and said notch means are defined by said fingers, said fingers being normally biased into tray side portion engaging positions to hold and stabilize a tray to prevent it from tipping and being biasable outwardly out of engagement with said side portions.
 20. A food holding cabinet in accordance with claim 18 further including a plurality of vertically superposed trays supported on said tray supporting elements, each said tray having spacer means positioned closely adjacent the next upper tray and engaging and lifting the next upper tray when said elevator means is elevated. 